There are different types of devices used to control the level of polluting gases exiting from the exhaust of an internal combustion engine. Such pollution control devices include catalytic converter, diesel particulate and other engine exhaust filters or traps, as well as devices that combine both catalytic and filtering or trapping functions. Various techniques for assembling such pollution control devices are known. Each of these techniques include mounting (i.e., canning) a pollution control element (e.g., a catalytic element, exhaust filter, etc.) within a housing, by positioning the pollution control element inside of the housing and disposing a mounting material, typically in mat or sheet form, in the gap between the pollution control element and the housing. The sheet-shaped mounting mats are wrapped around the exterior of the pollution control element. Mounting materials have also been molded into a cylindrical or tubular shaped mounting mat and slipped over the pollution control element, or insert molded around the pollution control element (e.g., a monolithic catalytic element). After the mounting mat is disposed around the pollution control element, the resulting assembly is canned. Conventional canning techniques include the use of mechanical stuffing (e.g., using a stuffing cone), tourniquet, and clamshell canning operations that result in the mounting mat being disposed within the gap between the can or housing and pollution control element.
The mounting material is required to apply sufficient mounting pressure to prevent movement of the pollution control element within the housing during the operation of the pollution control device. At the same time, pollution control elements are typically relatively fragile. Therefore, the pressure exerted by the mounting material must be kept low enough to prevent the pollution control element from being crushed. In addition, the gap between the housing and the pollution control element can change significantly during the operation of the pollution control device. This gap can also vary somewhat as the result of the differences in manufacturing tolerances and material choices between the pollution control element and the housing. As a result, the mounting material also needs to be resilient enough to maintain an acceptable level of mounting pressure as this gap changes.
There is a continuing need for improving such mounting techniques and for mounting materials that not only exhibit the mounting properties desired, but also facilitate the mounting of a pollution control element inside a corresponding pollution control device housing. The present invention provides a new mounting mat and technique for mounting a pollution control element in a housing of a pollution control device.